This invention relates to a pigment toner and to a process for its manufacture. More particularly, the invention relates to an improved Alkali Blue pigment toner characterized by soft texture and high tinting strength and to a process for its manufacture.
"Alkali Blue" is generally known in the art as, and is used herein to define, an arylpararosaniline sulfonic acid of the general formula ##STR1## wherein R may be hydrogen, chlorine, bromine, alkyl containing from 1 to 4 carbon atoms, alkoxy containing from 1 to 4 carbon atoms, nitro-, amino-, sulfonamidealkylamino containing from 1 to 4 carbon atoms, R.sub.1 and R.sub.2 may be hydrogen, or alkyl containing from 1 to 4 carbon atoms, R.sub.3 may be hydrogen or phenyl with or without a grouping such as R and X may be hydrogen, chlorine, bromine, SO.sub.3 H or COOH.
A process for converting aryl pararosaniline sulfonic acid dyestuffs into soft textured pigments with high tinctorial strength is outlined in U.S. Pat. No. 3,582,381. The method calls for obtaining a fine aqueous suspension of the dyestuff which is subsequently treated at elevated temperatures (80.degree. to 100.degree. C.) with an aqueous emulsion (O/W emulsion) of natural or synthetic vehicles prepared by known methods using emulsifying agents and/or high speed equipment such as dissolvers, homogenizers, and colloid mills. The slurry is then suction filtered, washed and dried at lower temperatures (50.degree. to 80.degree. C.).
U.S. Pat. No. 3,712,824 uses a similar method with an emulsion made using a varnish comprised of (a) a water immiscible organic liquid with a high boiling point, (b) a resin which is compatible with the organic liquid used and (c) an organic sovent insoluble in water but which can solubilize or swell the resin. The varnish-emulsion prepared using emulsifying agents and/or a homogenizer is mixed with the pigment slurry and the mixture further agitated in a high speed agitator such as a dissolver to obtain a foamy mass which is dried in vacuum or by hot air (50.degree. to 80.degree. C.) to obtain an easily dispersible pigment.
A somewhat modified method is outlined in U.S. Pat. No. 4,032,357 where no separate emulsion is prepared. The pigment is coprecipitated with one or more anionic surfactants (in situ emulsifiers) and the resulting slurry is mixed with a hydrophobic oil phase, vigorously stirred and heat treated (if needed) to obtain a coated presscake which on drying (70.degree. to 80.degree. C.) yields a soft textured pigment.
U.S. Pat. No. 3,635,745 discloses a process for preparing coloristically valuable pigments by dissolving the pigment in an alkali solution and an additive. The additives that may be employed include "tall resin." The pigment can be precipitated from the alkaline solutions by the addition of acids.
In general the prior art methods involve two or more steps and call for the us of surfactant(s) treated pigments or emulsifying agents to make emulsions and high speed equipment to transfer the pigment from aqeuous into the oil phase. Accordingly, it is a purpose of the instant invention to provide a process for preparing soft textured, high strength Alkali Blue toners wherein little or no external energy is needed for emulsification thus simplifying the process by eliminating the need for high speed equipment as well as the need for added surfactants.